In the production technology in the field of integrated circuit in an electronics industry, demand for high integration and high speed has been increasing. With respect to silicon ULSI, particularly logic ULSI, performance of the wiring which connects MOSFET, rather than the performance of MOSFET itself by its miniaturization has been problematic. Namely, in order to solve the problem of wiring delay due to multilayer interconnect, reduction of wiring resistance and reduction of capacity between wirings and between layers have been required.
Accordingly, at present, introduction of copper wiring having a lower electric resistance and having a migration resistance, instead of aluminum wiring used for the most part of the integrated circuit, is essential, and a process comprising seed formation by sputtering or chemical vapor deposition (hereinafter referred to simply as CVD) method, followed by copper plating, has been used practically.
As the low dielectric constant interlayer insulating film material, various ones have been proposed. Heretofore, as the inorganic system, silicon dioxide (SiO2), silicon nitride and phosphosilicate glass, and as the organic system, polyimides have been employed. In recent years, with a purpose of obtaining a more homogeneous interlayer insulating film, it has been proposed that a tetraethoxysilane monomer is preliminarily hydrolyzed, i.e., subjected to polycondensation to obtain SiO2, which is used as a coating material called “spin on glass” (inorganic SOG), and it has been proposed to use a polysiloxane obtained by polycondensation of an organoalkoxysilane monomer as organic SOG.
Further, as a method of forming the insulating film, there are two methods including a coating method comprising coating an insulating film polymer solution by e.g. spin coating to carry out film formation and a CVD method comprising plasma polymerization mainly in a plasma CVD equipment to carry out film formation.
As the plasma CVD method, for example, JP-A-2002-110670 proposes a method of forming an oxidized trimethylsilane thin film from trimethylsilane and oxygen by the plasma CVD method. Further, JP-A-11-288931 proposes a method of forming an oxidized alkylsilane thin film from an alkoxysilane having a straight chain alkyl group such as methyl, ethyl or n-propyl, an alkynyl group such as vinyl phenyl and an aryl group, by the plasma CVD method. An insulating film formed by such conventional plasma CVD material has favorable adhesion properties to a barrier metal and a copper wiring material which is a wiring material, on the contrary, uniformity of the film may be problematic, or the film deposition rate or the dielectric constant may be insufficient in some cases.
On the other hand, the film formed by the coating method has favorable uniformity, however, three steps of coating, solvent removal and heat treatment are required, such being economically disadvantageous as compared with a film formed by the CVD method. Further, adhesion properties to a barrier metal and a copper wiring material which is a wiring material, and uniform coating itself of the coating liquid to a miniaturized substrate structure tend to be problematic in many cases.
Further, with respect to the materials in the coating method, a method of making materials be porous has been proposed so as to achieve an ultra low-k material having a dielectric constant of at most 2.5, more preferably at most 2.0. A method of dispersing organic component fine particles which are easily pyrolyzed into an organic or inorganic material matrix, followed by heat treatment to make the material be porous, and a method of depositing SiO2 ultrafine particles formed by evaporation of silicon and oxygen in a gas, to form a thin film of SiO2 ultrafine particles, may, for example, be mentioned.
However, although these methods of making the material be porous, are effective to achieve a low dielectric constant, mechanical strength tends to decrease, whereby chemical mechanical polishing (CMP) may be difficult, or increase of the dielectric constant and wiring corrosion due to absorption of moisture may be caused in some cases.
Accordingly, the market further requires a well-balanced material which satisfies all the requirements such as a low dielectric constant, an adequate mechanical strength, adhesion properties to a barrier metal, prevention of copper dispersion, plasma ashing resistance and moisture absorption resistance. In order to satisfy these requirements to a certain extent, an organosilane type material having an increased proportion of carbon in the organic substituent to silane, thereby having characteristics intermediate between the organic polymer and the inorganic polymer has been proposed.
For example, JP-A-2000-302791 proposes a method to obtain an interlayer insulating film not being porous and having a dielectric constant of at most 2.4, by using a coating solution obtained by hydrolysis and polycondensation of a silicon compound having an adamantyl group by a sol-gel method in the presence of an aqueous acid solution.
However, this material is a material for the coating method, and there are still problems of the above-described film formation method by the film coating method.